I agree the phoneme editor works very well. And behaves really well during copying, pasting and editing already existing phoneme keys
Default mouth shape is best open, for exactly the reasons you gave.
the transitions are smoother and it covers up slightly inexact timing
(maybe not quite as open as peters tho)
I had a character with no teeth, and needed them for 'f, and s and other 'teethy' mouth shapes, so i made some teeth seperately, (new object), and added them to one of the figures headbones. (one that didn't move).
Then added morph targets to new teeth. Teeth Morphs were 'top up, bottom down, top out and bottom out.
As you will know, morph targets work both ways. Ie: open mouth morph can be used as closed mouth by going into negative values. Doesn't always suffice, but does more often than not.
So positive values raised teeth in 'top teeth up morph', and negative values lowered the top teeth. (kept things 'simpler')
Top teeth out was handy for 'F', because the teeth needed to poke out a bit to cover bottom lip. (a mixture of topteeth down and topteeth out)
It meant some extra morphing in scene mode, having to animate teeth seperately from mouth, but saved me losing all the existing morph targets i'd made, if i'd added teeth to the actual head object.
A tongue can also be added later in the same way. A seperate object added to the figure, and with it's own morphs, tongue up etc. I found 'tongue up worked best with just the front half of the tongue curling up. Then i had a morph target called 'tongue lift, which moved the whole tongue up and down.
Theres so much can be done with morph targets.
PeterTalking head is looking, and sounding, really good, and the more you keep at it, the better will be the results.
Good one
exile, keep up the good work.